In a simple embodiment of an electronic ballast in accordance with the prior art, the dimming value is set via a unidirectional dimming interface, for example a 1 . . . 10 V interface. In the case of this interface, the dimming value is defined via the level of a voltage that is present across two dimming value control inputs of the interface, or via the level of a current that flows over the interface.
For DALI devices (DALI standing for “Digital Addressable Lighting Interface”) there are bidirectional dimming interfaces which generally operate digitally, as an alternative to the unidirectional dimming interface. Consequently, a dimming value control input must be sent a binary number for controlling the dimming value, by way of example a “0” standing for a switched-off lamp, and the numbers 1 to 254 being dimming values that determine the brightness of the lamp.
Both the stipulation of the dimming value via the level of a voltage or a current intensity, and the stipulation of the dimming value via a digital command are technically complicated. In particular, a respective electronic ballast specifically needs to be provided with a suitable control unit that undertakes the settings of the voltage or the current or outputs digital control signals.
The detection of lamp faults has also been performed to date with the aid of digital signals. This also appears to be troublesome, particularly as regards evaluation.